284 



greenish gray, or mountain green, containing 

 long crystals of vitreous feld-spar, appears ex- 

 posed. It is the real porphyrschiefer of Werner; 

 and it would be difficult to distinguish, in a 

 collection of stones, the phonolite of Parapara 

 from that of Bilin in Bohemia. It does ndt 

 however here form rocks with grotesque shapes, 

 but little hills covered with tabular blocks, large 

 plates extremely sonorous, translucid on the 

 edges, and wounding the hands when broken. 



Such are the successions of rocks, which I 

 described on the spot, as I progressively found 

 them, from the lake of Tacarigua to the entrance 

 of the steppes. Few places in Europe display a 

 geological constitution so well worthy of being 

 studied. We saw there in succession six for- 

 mations : 



mica-slate gneiss; 

 green slate (transition) ; 

 black limestone (transition) ; 

 serpentine and gruenstein ; 

 amygdaloid (with pyroxene) ; and 

 phonolite. 



I must observe in the first place, that the sub- 

 stance, which we have just described under the 

 name of gruenstein, in every respect resembles 

 that, which forms layers in the mica-^slate of 

 Cape Blanc, and veins near Caraccas *. It dif- 



* See above/ vol. iii, p. 405; and p. 59 of the present 

 volume. 



